A French court on Thursday told Twitter to identify people who had posted anti-Semitic and racist entries on the social network. Twitter is not sure it will comply. And the case is yet another dust-up in the struggle over speech on the Internet, and which countries’ laws prevail.
The court order came in a lawsuit brought by French groups who said the Twitter postings, which were made under pseudonyms, broke French law against racist speech. Twitter has said that under its own rules, it does not divulge the identity of users except in response to a valid court order in the United States, where its data is stored. Twitter has already removed some of the content at issue from its site in France, in keeping with company policy to remove posts in countries where they violate the law.

On Thursday, Twitter said in a brief statement that it would review its legal options after the French ruling; officials at the company’s San Francisco headquarters did not respond to numerous requests for comment.

It remains unclear whether French prosecutors will press their case across the Atlantic and force Twitter’s hand in an American court under a time-consuming process detailed in a so-called mutual legal assistance treaty.

The case revolves around the broad question of which country’s laws have jurisdiction over content on the Internet. This question has become increasingly complicated as vast piles of information are stored in sprawling data centers, known as the cloud, that are accessible over the Internet anywhere, anytime.

“It is a big deal because it shows the conflict between laws in France and laws in the U.S., and how difficult it can be for companies doing business around the world,” said Françoise Gilbert, a French lawyer who represents Silicon Valley companies in courts on both continents.

In this case, the jurisdictional issue has an additional wrinkle because Twitter does not have an office in France and does not face the prosecution of its employees here, a problem that other Web companies, like Facebook and Google, have faced elsewhere. Twitter is popular in France, nonetheless. It is available to anyone with an Internet connection and sells ads on its site here. This could embolden French authorities to try to apply its laws to the service.

With 200 million users, most of them outside the United States, Twitter has confronted these conundrums over hate speech and free expression before, especially in Europe.

In October, at the request of the German government, Twitter blocked users in Germany from access to the account of a neo-Nazi group banned there. It was the first time Twitter acted on a policy known as “country-withheld content,” announced last January, in which it agreed to block an account at the request of a government.

In 2011, British authorities went to court in California to extract information about a Twitter user who went by the pseudonym Mr. Monkey and was accused of defaming members of a British town council. The company complied.

Twitter says in its online help center that foreign law enforcement agencies can seek user data through what is known as a “mutual legal assistance treaty.”

“It is our policy to respond to such U.S. court-ordered requests when properly served,” the company says on the site.

But Twitter is not the only Web company facing government requests for personal data. Google said this week that it received more than 21,000 requests in the last six months; more than 8,000 from the United States, which was followed by India, France, Germany and Britain.

Twitter, though, has sought to cast itself as a special defender of free speech, sometimes describing it as a competitive advantage. On occasion, it has fought unsuccessful battles with prosecutors in the United States seeking to extract data on Twitter users.

The French case is also part of a brewing fight between the United States and Europe over the data controlled by American Web companies and stored in the cloud. European lawmakers worry about American companies sharing data about Europeans with the United States government under American laws that authorize surveillance on foreign citizens. This case flips that objection on its head, with European authorities seeking information on its citizens from an American company.

Chris Wolf, an American lawyer who was in Brussels this week at a conference debating European data protection laws, said it was proving difficult to interpret jurisdiction laws in the digital age.